Partisan gerrymandering, which states have the biggest gap between voter percentage and House seats held

1. Why “biggest gap” depends on the metric you pick

There is no single, universally accepted way to turn votes into a “should‑have” number of seats; scholars and advocacy groups use multiple measures — the efficiency gap, partisan bias, mean‑median, declination and PlanScore’s composite — and each highlights different features of a map, so the state that looks worst under one metric may not under another ^{[4] [5] [1]}.

2. Examples often cited: Texas and California, but for different reasons

Analysts point to Texas as a plan that yields more Republican seats than its major‑party vote would suggest (Republicans won 66% of House seats on 56% of the vote in an example cited), while California in some cycles produced a large Democratic seats‑bonus (Democrats 83% of seats on 61% of the vote in one referenced analysis) — yet authors note the contrast can reflect partisan competition and geography as much as map‑drawing intent ^[1].

3. Geography, clustering and “winner’s bonus” complicate blame

A “modest” mismatch between seats and votes is normal: the expected winner’s bonus means a party’s seat share may rise faster than its vote share (one common benchmark assumes ~2% seat gain per 1% vote gain). Also, Democrats’ urban concentration can produce natural skew toward Republicans in many states even without intentional packing/cracking, so map effects must be separated from demographic geography ^{[1] [2]}.

4. Courts, politics and where the sharpest fights are happening

Court challenges — especially around race‑based lines — have kept states like Texas in litigation and spotlighted maps that courts say were problematic; a federal panel blocked a Texas map as racially gerrymandered in recent reporting, underscoring how legal rulings can change which maps are in effect and therefore which seat‑vote gaps matter ^{[6] [7]}.

5. State‑level studies and trackers point to consistent trouble spots

Project‑level tools and trackers aim to quantify partisan advantage by state. The Princeton Gerrymandering Project and Michigan State’s Partisan Advantage Tracker, and services such as PlanScore, produce state rankings and identify which enacted plans favor one party — they show recurrent advantages in states where one party controlled the process ^{[8] [5] [4]}.

6. What journalists and scholars watch to attribute cause vs. consequence

To decide whether a gap is a “gerrymander,” analysts compare enacted maps to neutral or randomly generated maps, examine whether seats exceed what random maps produce, and measure whether lines reach into demographically different areas to pick off voters. Harvard analysts emphasize comparing enacted maps to ensembles of non‑partisan maps to detect intentional advantage ^[2].

7. Competing viewpoints: partisan advantage vs. unavoidable distortion

Advocates like the Brennan Center highlight examples (e.g., North Carolina) where maps produce seat counts far out of line with statewide preferences and call that engineered advantage; other analysts (and some neutral metrics) caution that some disparity arises from lawful factors — incumbent protection, communities of interest, geography — and that modest gaps alone aren’t definitive proof of illicit gerrymandering ^{[3] [1]}.

8. Practical takeaway for someone comparing states

If you want a reproducible list of “biggest gaps,” use a single measurement system (for example, the Partisan Advantage Tracker or PlanScore) and the same elections (which statewide vote totals to compare) across states; expect the ranking to change if you switch metrics or elections. The sources cited here point repeatedly to Texas, California, North Carolina and Wisconsin as frequent flashpoints, but emphasize methodological caveats and legal context ^{[5] [4] [3] [2]}.

Limitations and next steps: available sources do not provide a single, authoritative ranked list of states by seat‑vote gap in your query; to produce a reproducible ranking you’d need to select (and cite) a metric, a set of elections to aggregate, and a data source (PlanScore or the Partisan Advantage Tracker are ready‑made choices) ^{[4] [5]}.